The present invention concerns an improved stabilizer concentrate for use in polymeric blend compositions. Specifically, the present invention concerns an improved stabilizer concentrate for use in polymeric blend compositions which blend compositions comprise a thermally sensitive polymeric material, particularly, a thermally sensitive interpolymer, for example a vinylidene chloride interpolymer or an ethylene-vinyl alcohol copolymer, and at least one other polymeric component.
Vinylidene chloride interpolymers are well-known in the prior art for their excellent barrier to the mass transport of atmospheric gases and moisture vapor. Because of their excellent barrier properties, vinylidene chloride interpolymers are well suited for use in food packaging operations and other similar operations, wherein it is desirable to protect a given article from oxygen and loss of moisture. Ethylene-vinyl alcohol copolymers (EVOH) are also well-known in the art for their high barrier to the transportation of oxygen. EVOH copolymers are suitable for food packaging in which it is desirable to protect the packaged product from oxygen. Due to their high moisture sensitivity, EVOH copolymers must ordinarily be isolated from moisture in the atmosphere and/or the food product by outer layers of at least one other polymeric component which provides a high barrier with respect to moisture.
In forming containers suitable for use in food packaging applications, it is common to employ a layer of a thermally sensitive barrier polymer in a multi-layer structure, thus providing a structure which is possessed of good oxygen and water vapor barrier properties. For example, it has proven desirable to form barrier containers and films out of a multi-layer structure comprising two outer layers of a polymeric material possessed of desirable processing properties and at least one inner layer of a vinylidene chloride or ethylene-vinyl alcohol interpolymer. Such multi-layer structures may be formed through laminating processes or through a process of coextrusion or other similar process which are well-known in the art.
Processes for forming and using multi-layer structures such as those described above inherently produce a certain amount of scrap material. From an economic standpoint, it is desirable to employ this scrap material in a useful manner. In the past, this has proven difficult since the scrap material comprises a thermally sensitive polymer and at least one other polymer which usually forms the outer layers of the multi-layer structures. Typically, the polymeric material which comprises the non-barrier layers of the multi-layer structure has processing properties which are quite different from the thermally sensitive barrier polymer. Attempts to reprocess or recycle the scrap material have proven to be difficult and somewhat unsatisfactory because reprocessing of the scrap material typically leads to an unacceptable degree of degradation of the thermally sensitive barrier polymer.